Self-locking gripping head

ABSTRACT

A power-operated gripping head for lifting workpieces includes two pivotally mounted coacting jaws which are moved toward and away from each other by a pair of pivotal levers forming with a linearly movable actuator a toggle linkage which will lock the jaws in closed position.

llnited States Patent [7 2] inventor Bruno Jacksch Wiesbaden, Germany [21] Appl. No. 22,435 [22] Filed Mar. 25, 1970 [45] Patented Dec. 28, 1971 [73] Assignee Firma W & M Automation Karl Muller Wiesbaden, Germany [32] Priority Nov. 12, 1969 [3 3] Germany [31] Pl958827.3

[54] SELF-LOCKING GRIPPING HEAD 5 Claims, 3 Drawing Figs.

[52] U.S. Cl 294/88, 294/106 Primary Examiner-Even C. Blunk Assistant Examiner--I. Kenneth Silverman AttarneyChristen & Sabol ABSTRACT: A power-operated gripping head for lifting workpieces includes two pivotally mounted coaeting jaws which are moved toward and away from each other by a pair of pivotal levers forming with a linearly movable actuator a toggle linkage which will lock thejaws in closed position.

Gripping heads used in installations for lifting, transporting and depositing workpieces are known in which a pair of coacting pivotal jaws fastened on shafts and moved by a power actuator to pick up the workpieces, transport them and then deposit them again. These gripping heads have the disadvantage that when the jaws are loaded and the supply of actuator power fails, the jaws slowly open and the workpiece drops down. The dropping of the workpiece may result in injuries to personnel and in damage to equipment from which the workpieces have been lifted or on which they are to be deposited.

The purpose of this invention is to create a gripping head the jaws of which, when loaded, cannot by themselves open when the power supply fails.

This is essentially effected on gripping heads for lifting, transporting and depositing workpieces where the head's jaws are fastened on a pair of parallel shafts and are activated by locking levers mounted on the same shafts which, in turn, are moved by a power actuator as follows: Between the pivotal locking levers there is a linearly reciprocable power actuator connected with the locking levers by a pair of toggle links. When the jaws are open and the actuator is in its initial position the links are angularly disposed with respect to each other but, as the jaws approach their closed position the pivot points of the links approach a straight line until they finally lie in a plane disposed normal to the direction of movement of the actuator, at which time a torsional force is exerted in the shafts connecting the respective locking levers and jaws. A slight further movement of the actuator will move the pivot points of one end of the links past their dead center lines and the jaws will be effectively locked. If in a gripping head of this type the actuator power fails while the jaws are carrying a load, the weight of the workpiece urges the jaws in an outward direction and the locking levers in the direction towards the actuator. The actuator cannot yield to the pressure because the direction in which the pressure of the locking levers acts on it is at right angles to the direction of the movement of the actuator and there is no pressure component which can move the actuator in the direction required for opening of the jaws.

Further characteristics of the invention are described in the description of the figures and in the annexed claims.

In FIGS. 1 to 3 the invention is represented in a preferred form of application as an example; the invention, however, is not limited to this one form of application.

FIG. 1 shows a vertical section through a gripping head according to the invention parallel to a shaft which carries the jaws on line A-A of FIG. 3

FlG. 2 shows a vertical section on line BB of FIG. 1 and FIG. 3 is a side view of the gripping head at right angles to the shafts carrying the jaws.

In the figures numeral 35 indicates generally a power actuator means, in this case a hydraulic cylinder with the piston rod 28 projecting downwardly. Numeral 1 indicates a plate positioned perpendicularly to the direction of motion of the piston rod 28. Below this plate the parts which are positioned between piston rod 28 and gripping jaws 52 are mounted. The end of the hydraulic cylinder 35 which extends away from rod 28 and plate 1 are fastened in a supporting frame which is not shown. The free end of piston rod 28 extends through a recess 53 in plate 1. Below plate 1, on the free end of the piston rod 28 a slotted member 25 is fastened. Under plate l, on each of the opposite sides thereof four aligned bearing plates 5 are fastened, for example, with screws. in the two outside bearing plates 5 in the lower ends of each two gripping jaw carriers 8 and 9 with lateral studs are mounted rotatably in bearings 7. Between the two bearing plates 5 in the center adjacent the piston rod 28 locking levers 19 are positioned, with lateral studs which are rotatable in bearings 7 at the lower ends of these two center bearing plates 5. Shaft 18 carries the two jaw carriers 8 and 9 and the locking lever 19, in fixed alignment. This shaft is, preferably, in the form of a polygonal shaft, particularly a square shaft in order to assure that it cannot turn with res ct to the jaw carriers 8 and 9, or with respect to the locking ever 19. It 18 also of advantage to make this shaft 18 a torsion rod which may be tightened by an additional short stroke of the working cylinder 35 when the jaws 52 are in closed position.

The locking levers 19 are bifurcated to provide on top a forked portion in which one end of a link 23 rotatably fastened by means of a bolt 22. The other end of this link is fastened with a similar bolt 22 to the slotted member 25 which is mounted on the free end of the piston rod 28. When the jaws 52 are in closed position the pivot points formed by bolts 22 between locking lever 19 and member 25 are situated in a plane which lies perpendicularly to the direction of movement of the piston rod 28, and when the pivot point between slotted member 25 and link 23 is moved a short distance downwardly beyond the plane lying perpendicularly to the direction of movement of piston rod 28 the toggle links 23 will effectively lock the locking levers in position.

The jaws 52 are fastened to the carriers 8 and 9 respectively by screws 1 l, and it is possible at the front side of bearings 5 to adjust the screws 14 by turning adjusting nuts 15 so as to vary the angular relation between coacting jaws 52. The open angle between the jaws 52 can be changed by changing the longitudinal drawout distance of the piston rod 28. For replacing of the jaws 52 only the screw 1 1 has to be loosened. An eccentric closing of the jaws 52, if the grab head is constructed according to the invention, is not possible.

The two pairs of jaws 52 clamp down on a workpiece faultlessly even if the diameters of the workpiece deviate at one or both gripping points from the specified size, as it is usually the case in unmilled workpieces, according to the design of the jaws differences in diameter up to 5 mm. can be accommodated without readjustment of the nippers or loss of the automatic stopping device's action.

Other modifications and improvements may be made by those skilled in the art which would come within the scope of the annexed claims.

I claim:

1. In a gripping head for lifting, transporting and depositing workpieces, the combination including a mounting plate, a pair of spaced parallel shafts rotatably mounted on said plate, a pair of coacting gripping jaws attached respectively to said shafts for pivotal movement toward and away from each other, a pair of locking levers connected respectively with said shafts for rotating said jaws, power actuator means connected with said mounting plate and including a linearly reciprocable rod positioned for movement in a plane disposed between and normal to the plane of said pair of shafts, a pair of links each connected pivotally at one end to said rod the other end of each link being connected pivotally to a respective one of said locking levers at points spaced from said shafts, said links and locking levers comprising toggle linkage means whereby movement of the rod in one direction will open the jaws and movement of the rod in the opposite direction will close the jaws and said links when said jaws are closed will be disposed substantially in a plane normal to the plane of movement of the rod.

2. The invention defined in claim 1, wherein said power actuator means includes means for moving said linearly reciprocable rod in said opposite direction slightly past the position in which said links are disposed in said normal plane to lock said jaws.

3. The invention defined in claim 1, wherein said power actuator means comprises a hydraulic cylinder and said linearly reciprocable rod includes a piston movable in said cylinder.

4. The invention defined in claim 1, wherein said linearly movable rod includes a slotted member, and one end of each of said pair of links is pivotally connected at spaced axes with said slotted member.

5. The invention defined in claim 1, wherein each of said pair of locking levers is connected to a respective shaft axially spaced from a respective gripping jaw attached to said shaft, whereby torsional force may be exerted in said shaft. 

1. In a gripping head for lifting, transporting and depositing workpieces, the combination including a mounting plate, a pair of spaced parallel shafts rotatably mounted on said plate, a pair of coacting gripping jaws attached respectively to said shafts for pivotal movement toward and away from each other, a pair of locking levers connected respectively with said shafts for rotating said jaws, power actuator means connected with said mounting plate and including a linearly reciprocable rod positioned for movement in a plane disposed between and normal to the plane of said pair of shafts, a pair of links each connected pivotally at one end to said rod the other end of each link being connected pivotally to a respective one of said locking levers at points spaced from said shafts, said links and locking levers comprising toggle linkage means whereby movement of the rod in one directiOn will open the jaws and movement of the rod in the opposite direction will close the jaws and said links when said jaws are closed will be disposed substantially in a plane normal to the plane of movement of the rod.
 2. The invention defined in claim 1, wherein said power actuator means includes means for moving said linearly reciprocable rod in said opposite direction slightly past the position in which said links are disposed in said normal plane to lock said jaws.
 3. The invention defined in claim 1, wherein said power actuator means comprises a hydraulic cylinder and said linearly reciprocable rod includes a piston movable in said cylinder.
 4. The invention defined in claim 1, wherein said linearly movable rod includes a slotted member, and one end of each of said pair of links is pivotally connected at spaced axes with said slotted member.
 5. The invention defined in claim 1, wherein each of said pair of locking levers is connected to a respective shaft axially spaced from a respective gripping jaw attached to said shaft, whereby torsional force may be exerted in said shaft. 